Increased nutrient supply facilitates acclimation to high-water level in the marsh plant Deyeuxia angustifolia: The response of root morphology

Both water level and nutrient availability are important factors influencing the growth of wetland plants. Increased nutrient supply might counteract the negative effects of flooding on the growth of the fast-growing species. Experimental evidence is scarce and the mechanism is far from clear. The aim of this study is to identify the role of nutrient availability in acclimation to high-water level by investigating the growth and root morphology of the marsh plant Deyeuxia angustifolia, one of the dominant species in the Sanjiang Plain, China. Experimental treatments included two water levels (0 and 10 cm, relative to soil surface) and three levels of nutrient supply (0, 0.5 and 1 g fertilizer per container). High-water level usually led to decreased biomass accumulation, shoot mass and root mass, whereas biomass accumulation was unaffected by water level at the highest nutrient level, indicating that high-nutrient availability played a role in compensating for the growth loss induced by the high-water level. Increased nutrient supply led to decreased root length in 0 cm water-level treatments, but root length increased with nutrient supply in the 10 cm water-level treatments. High-water level usually led to a lower lateral root density, lateral root:main root length ratio and the diameter of main roots and laterals, whereas increased nutrient supply resulted in thicker main roots or laterals, and a higher total root length, lateral root density and lateral root:main root length ratio. These data indicate that the growth of D. angustifolia is restrained by high-water level, and that increased nutrient supply not only ameliorates root characteristics to acclimate to high-water level but also results in a high-total root length to facilitate nutrient acquisition.     

基于不同零模型的三江平原沼泽湿地主要物种小尺度点格局分析

在三江平原沼泽湿地,基于不同零模型的点格局方法,研究了常年积水环境条件下沼泽湿地主要优势种毛苔草、漂筏苔草、狭叶甜茅以及小叶章种群的空间分布格局特征。结果表明:在0—200cm尺度范围内4种物种基本都偏离完全随机模型,表现为聚集分布,但偏离的程度不同;除了数量最少的小叶章种群外,其他3种物种都在一定尺度上偏离了泊松聚块模型;毛苔草和狭叶甜茅种群在极小尺度上偏离嵌套双聚块模型,但不显著,而漂筏苔草种群在所有尺度上符合嵌套双聚块模型。种群的实测值偏离完全随机模型的程度越大,越有可能符合符合泊松聚块模型,偏离泊松聚块模型的程度越大,越有可能符合嵌套双聚块模型。4种物种在0—200cm尺度范围内形成的聚块是由营养繁殖引起的,多个分株系统组成大聚块,而每个分株系统形成一个小聚块,聚块的形成加剧了种内竞争,使得种群的聚集强度降低。     

Zonation of plant cover and environmental factors in wetlands of the Sanjiang Plain,northeast China

The zonation of depressional and riparian wetlands in the Sanjiang Plain of northeastern China was studied to describe their vegetation composition and environmental variables. We sampled 108 plots in 6 depression and riparian wetlands. Samples were classified into 4 groups using two‐way indicator species analysis (TWINSPAN). Emergent marsh vegetation was characterized by Carex lasiocarpa and C. pseudocuraica, meadow marsh vegetation by tussock species such as Carex appendiculata and C. meyeriana, wet meadow vegetation by Calamangrostis angustifolia and Carex appendiculata, and shrub meadow vegetation by the shrubs Betula fruticosa, Alnus sibirica and Salix rosmarinifolia and the graminids Carex schmidtii and Calamagrostis angustifolia. CCA ordination showed that water table, organic matter and available N were the major factors explaining the vegetation zonation pattern. Compared with other Northern Hemisphere regions, bog and fen vegetation are completely absent due to climatic conditions unfavorable for peat formation. Out of four vegetation types, only the Carex lasiocarpa community and the C. pseudo‐curaica community have been found in other regions. However, at the species level many species are widespread and some species are vicariant or pseudovicariant to other regions in the world. Our study suggests that topography and hydrology may be the most important determinants of the vegetation pattern in this region.     

Response of Two Dominant Boreal Freshwater Wetland Plants to Manipulated Warming and Altered Precipitation

This study characterized the morphological and photosynthetic responses of two wetland plant species when they were subject to 2–6°C fluctuations in growth temperature and ±50% of precipitation, in order to predict the evolution of natural wetlands in Sanjiang Plain of North-eastern China. We investigated the morphological and photosynthetic responses of two dominant and competitive boreal freshwater wetland plants in Northeastern China to manipulation of warming (ambient, +2.0°C, +4.0°C, +6.0°C) and altered precipitation (−50%, ambient, +50%) simultaneously by incubating the plants from seedling to senescence within climate-controlled environmental chambers. Post-harvest, secondary growth of C. angustifolia was observed to explore intergenerational effects. The results indicated that C. angustifolia demonstrated a greater acclimated capacity than G. spiculosa to respond to climate change due to higher resistance to temperature and precipitation manipulations. The accumulated effect on aboveground biomass of post-harvest secondary growth of C. angustifolia was significant. These results explain the expansion of C. angustifolia during last 40 years and indicate the further expansion in natural boreal wetlands under a warmer and wetter future. Stability of the natural surface water table is critical for the conservation and restoration of G. spiculosa populations reacting to encroachment stress from C. angustifolia expansion.     

Root aerobic respiration and growth characteristics of three Typha species in response to hypoxia

The responses of root aerobic respiration to hypoxia in three common Typha species were examined. Typha latifolia L., T. orientalis Presl, and T. angustifolia L. were hydroponically cultivated under both aerobic and hypoxic growth conditions to measure root oxygen consumption rates. Hypoxia significantly enhanced the root aerobic respiration capacity of the two deep-water species, T. orientalis and T. angustifolia, while it did not affect that of the shallow-water species, T. latifolia. T. angustifolia increased its root porosity and root mass ratio, while T. latifolia increased its root diameter under the hypoxic growth conditions. The relative growth rates in biomass of T. orientalis and T. angustifolia were 59 and 39% higher, respectively, under the hypoxic growth conditions than under the aerobic growth conditions. In contrast, that of T. latifolia did not differ between the two conditions. In T. orientalis and T. angustifolia, enhanced root aerobic respiration rates under the hypoxic growth conditions would have increased the nutrient uptake, and thus higher relative growth rates were obtained. For the deep-water species, T. orientalis and T. angustifolia, the root aerobic respiration capacity was enhanced, probably in order to maintain the generation of respiratory energy under hypoxia.     

Root growth dynamics of Deyeuxia angustifolia seedlings in response to water level

A greenhouse experiment was performed to investigate root growth dynamics, plant growth, root porosity and root morphology of a marsh plant Deyeuxia angustifolia, one of the dominant species in the Sanjiang Plain, China. The aim of this study was to elucidate how this plant adjusts its root system to acclimate to different hydrological environments. Experimental treatments included three water depths: −5, 0 and 5 cm (relative to the soil surface). Biomass accumulation was higher in the −5 cm (0.90 g per plant) and 0 cm water-depth (1.18 g per plant) than that in the 5 cm water-depth treatments (0.66 g per plant), indicating that plant growth was inhibited in the high water level. Root:shoot ratio (0.67 versus 0.42–0.43), the length (16 cm versus 12–13 cm) and diameter of adventitious roots (0.47 mm versus 0.41 mm), and root number (167 versus 81–119 number of roots per plant) were higher in the 0 cm water-depth than those in the high and low water-depth treatments. Enhanced water level led to slightly increased porosity of main roots, but porosity was about 7% in all treatments. After 8 weeks, roots had been distributed into 14, 11 and 7 cm soil depth in the 0, −5 and 5 cm water-depth treatments, respectively, indicating that both high and low water levels led to shallow root systems. Our data suggest that D. angustifolia can adjust root morphology and root growth pattern according to water level, and that this plant has limited oxygen diffusion potential to the roots due to the reduced biomass in the high water level.     

Plant distribution can be reflected by the different growth and morphological responses to water level and shade in two emergent macrophyte seedlings in the Sanjiang Plain

In the Sanjiang Plain (North East China), narrowleaf small reed (Deyeuxia angustifolia) usually distributes widely in typical meadow or marsh, while reed (Phragmites australis), the concomitant species, is distributed sparsely in the D. angustifolia communities or relative open sites. To date, the mechanisms responsible for their different distribution patterns are far from clear. Both water level and light are important factors determining plant distribution in wetland ecosystems and therefore, the aim of this paper was to identify the role of these two factors and their potential interaction on plant distribution in this plain. Growth responses and biomass allocation of the two macrophytes were investigated by growing them in three irradiances (300, 100, 20 μmol m⁻² s⁻¹) and two water levels (0 and 5 cm) under greenhouse conditions. Biomass accumulation, mean relative growth rate (RGR), height and mean relative elongation rate (RER) of both species significantly decreased with the reduction of light availability. Biomass accumulation, RGR, height and RER of P. australis were significantly inhibited by higher water level. However, water level had no effect on the growth of D. angustifolia. Stem mass fraction was higher at 0-cm water level in D. angustifolia, and was not affected by water level in P. australis. These data suggest that D. angustifolia has a higher adaptive ability to acclimate to flooding and shade stresses than does P. australis, which might be an important reason for their different distribution patterns.     

Response of leaf, sheath and stem nutrient resorption to 7 years of N addition in freshwater wetland of Northeast China

Background and Aims

Increased N availability induced by agricultural fertilization applications and atmospheric N deposition may affect plant nutrient resorption in temperate wetlands. However, the relationship between nutrient resorption and N availability is still unclear, and most studies have focused on leaf nutrient resorption only. The aim of our study was to examine the response of leaf and non-leaf organ nutrient resorption to N enrichment in a temperate freshwater wetland.

Methods

We conducted a 7-year N addition experiment to investigate the effects of increased N loading on leaf, sheath and stem nutrient (N and P) resorption of two dominant species (Deyeuxia angustifolia and Glyceria spiculosa) in a freshwater marsh in the Sanjiang Plain, Northeast China.

Results

Our results showed that, for both leaf and non-leaf organs (sheath and stem), N addition decreased N resorption proficiency and hence increased litter N concentration. Moreover, the magnitude of N addition effect on N resorption proficiency varied with fertilization rates for D. angustifolia sheaths and stems, and G. spiculosa leaves. However, increased N loading produced inconsistent impacts on N and P resorption efficiencies and P resorption proficiency, and the effects only varied with species and plant organs. In addition, N enrichment increased litter mass and altered litter allocation among leaf, sheath and stem.

Conclusions

Our results highlight that leaf and non-leaf organs respond differentially to N addition regarding N and P resorption efficiencies and P resorption proficiency, and also suggest that N enrichment in temperate freshwater wetlands would alter plant internal nutrient cycles and increase litter quality and quantity, and thus substantially influence ecosystem carbon and nutrient cycles.     

Morphological responses of two plant species from different elevations in the Dongting Lake wetlands,China, to variation in water levels

The vegetation of wetlands show strong zonation patterns, but the mechanisms determining these patterns are not fully understood. In the present study, growth and morphological responses to a water level gradient (–20 cm (i.e. water level 20 cm below soil surface), –10 cm, 0 cm, 10 cm, 20 cm) were compared between a higher elevation plant (Imperata cylindrica) and a lower elevation plant (Carex brevicuspis) in the Dongting Lake wetlands of China. For both species, the aboveground, belowground, and total biomass were greater at –10 cm than at any other water level.. However, when the water level increased from –10 cm to 0 cm, there was a greater decrease in the biomass of I. cylindrica than in that of C. brevicuspis. Plant height, tiller number, leaf length, leaf width and leaf area showed greater variation along the water level gradient in I. cylindrica than in C. brevicuspis. Generally, with increasing water level, root length, rhizome number, and adventitious root biomass and number all decreased in I. cylindrica. However, in C. brevicuspis, neither the rhizome number nor the primary adventitious root biomass differed significantly among the five water levels. These results indicate that I. cylindrica have a lower tolerance for flooding and higher water sensitivity than C. brevicuspis and these differences may explain why I. cylindrica is found at relatively higher elevations that are not prone to flooding, while C. brevicuspis is found at comparatively lower elevations in the Dongting Lake wetlands.     

Ecotypic variation in root respiration rate among elevational populations ofAbies lasiocarpa andPicea engelmannii

Summary Small trees ofAbies lasiocarpa (Hook.) Nutt. andPicea engelmannii Parry were collected along two elevational transects in the central Rocky Mountains, and the effects of low temperature on their root respiration activity were measured after growth in cool and warm soil temperature treatments.Picea engelmannii roots respired significantly faster than those ofA. lasiocarpa, and trees of both species collected from high elevations respired significantly faster than those from lower elevations. The mean Q₁₀ and mean activation energy of respiration were 2.0 and 47.2 kJ mol^–1, respectively; they did not differ between transects, species, elevations of collection, or the soil temperature treatments. The results suggest ecotypic differentiation has occurred along these transects resulting in higher root respiration rates at higher elevations.     

Substrate and/or substrate-driven changes in the abundance of methanogenic archaea cause seasonal variation of methane production potential in species-specific freshwater wetlands

There are large temporal and spatial variations of methane (CH₄) emissions from natural wetlands. To understand temporal changes of CH₄ production potential (MPP), soil samples were collected from a permanently inundated Carex lasiocarpa marsh and a summer inundated Calamagrostis angustifolia marsh over the period from June to October of 2011. MPP, dissolved organic carbon (DOC) concentration, abundance and community structure of methanogenic archaea were assessed. In the C. lasiocarpa marsh, DOC concentration, MPP and the methanogen population showed similar seasonal variations and maximal values in September. MPP and DOC in the C. angustifolia marsh exhibited seasonal variations and values peaked during August, while the methanogen population decreased with plant growth. Methanogen abundance correlated significantly (P?=?0.02) with DOC only for the C. lasiocarpa marsh. During the sampling period, the dominant methanogens were the Methanosaetaceae and Zoige cluster I (ZC-Ι) in the C. angustifolia marsh, and Methanomicrobiales and ZC-Ι in the C. lasiocarpa marsh. MPP correlated significantly (P?=?0.04) with DOC and methanogen population in the C. lasiocarpa marsh but only with DOC in the C. angustifolia marsh. Addition of C. lasiocarpa litter enhanced MPP more effectively than addition of C. angustifolia litter, indicating that temporal variation of substrates is controlled by litter deposition in the C. lasiocarpa marsh while living plant matter is more important in the C. angustifolia marsh. This study indicated that there was no apparent shift in the dominant types of methanogen during the growth season in the species-specific freshwater wetlands. Temporal variation of MPP is controlled by substrates and substrate-driven changes in the abundance of methanogenic archaea in the C. lasiocarpa marsh, while MPP depends only on substrate availability derived from root exudates or soil organic matter in the C. angustifolia marsh.     

Combined effects between temporal heterogeneity of water supply,nutrient level,and population density on biomass of four broadly distributed herbaceous species

Temporal heterogeneity of water supply affects grassland community productivity and it can interact with nutrient level and intraspecific competition. To understand community responses, the responses of individual species to water heterogeneity must be evaluated while considering the interactions of this heterogeneity with nutrient levels and population density. We compared responses of four herbaceous species grown in monocultures to various combinations of water heterogeneity, nutrient level, and population density: two grasses (Cynodon dactylon and Lolium perenne), a forb (Artemisia princeps), and a legume (Trifolium repens). Treatment effects on shoot and root biomass were analyzed. In all four species, shoot biomass was larger under homogeneous than under heterogeneous water supply. Shoot responses of L. perenne tended to be greater at high nutrient levels. Although root biomass was also larger under homogeneous water supply, effects of water heterogeneity on root biomass were not significant in the grasses. Trifolium repens showed marked root responses, particularly at high population density. Although greater shoot and root growth under homogeneous water supply appears to be a general trend among herbaceous species, our results suggested differences among species could be found in the degree of response to water heterogeneity and its interactions with nutrient level and intraspecific competition.     

Comparisons of nutrient recovery and specific leaf area variation betweenCarex lasiocarpa var.occultans andCarex thunbergii var.appendiculata with reference to nutrient conditions and shading byPhragmites australis

The distribution of two sedge species was studied in two mires which differ in abiotic environments and in distribution ofPhragmites australis. Carex lasiocarpa var.occultans dominated in nutrient-poor valley mire, andCarex thunbergii var.appendiculata dominated in nutrient-rich flood plain subject to water fluctuations.Phragmites australis grew well in nutrient-rich conditions. The distribution ofC. lasiocarpa showed a strong negative correlation withP. australis coverage, whereasC. thunbergii coverage was not affected byP. australis. The leaf area per dry leaf mass (specific leaf area: SLA) ofC. thunbergii increased with shading byP. australis, but that ofC. lasiocarpa was stable. The SLA flexibility ofC. thunbergii to light interception might enable this species to invadeP. australis patches in nutrient-rich environments. The residual nutrient ratio of nitrogen and phosphorus (the ratio of the residual nutrient content at the end of the growing season to peak nutrient content) in the vegetative ramet ofC. thunbergii was 1.7 times higher than that ofC. lasiocarpa. This low residual ratio may indicate effective nutrient recovery to storage organs. The effective nutrient recovery inC. lasiocarpa might enable this species to grow even in nutrient-poor environments. However, it may be difficult forC. lasiocarpa to expand its habitat to nutrient-rich areas whereP. australis dominates as it is not shade tolerant.     

Growth rate, root development and nutrient uptake of 55 plant species from the Great Plains Grasslands, USA

Empirical and theoretical studies have highlighted that plantcompetition and species diversity are substantially affected by interactionsamong plant growth and nutrient uptake rates, root lateral spread, rootplasticity, and small scale soil nutrient heterogeneity. This study wasdesignedto (a) experimentally estimate parameters regarding rootscaling patterns, root biomass allocation, growth rates, nutrient productivity,and root nutrient influx rates of 55 plant species common to Great Plainsgrasslands; and (b) determine if grasses and forbs can beclassified into statistically distinct groups based on these characteristics.Wefound that: (1) In all species root lateral spread, rootlength, and root surface area had significant allometric scaling relationshipswith root biomass, but that the relationships were unaffected by Navailability.(2) Reductions in the supply of N increased the root:shootratio in 62% of the species. (3) The frequency distributionandmean values of maximum relative growth rates were very similar for grasses andforbs/shrubs, but mid successional grasses had a higher relative growth ratethan late successional ones. (4) In 78% of the species tested,N productivity was increased by reductions in the N supply.(5)When subjected to a high N supply, the N and P productivity of grasses was, onaverage, higher than that of forbs/shrubs, and the N and P productivity ofC₄ grasses was, on average, higher than that of C₃grasses. No differences were found under a low N supply. (6)Nodifferences on the average maximum N and P influx rates per unit of rootsurfacearea were found between grasses and forbs or between C₃ andC₄ grasses, but both were correlated with maximum relative growthrate. (7) The set of parameters we measured were able toseparate grasses and forbs/shrubs into statistically distinct groups that tendto follow in broad terms the coarse vs. fine scaleforaging strategies hypothesis.     

Effect of Root Cooling on Photosynthesis of Artemisia tridentata Seedlings under Different Light Levels

Root chilling has been shown to inhibit shoot photosynthesis yet the mechanism for such an action is not clearly understood. A study was designed to elucidate the mechanism by which root cooling may affect net photosynthesis. Roots of Artemisia tridentata seedlings were cooled from 20°C to 5°C while their shoot temperature remained at 20°C. This was conducted at two light levels (700 and 1300 μmol m^?2 s^?1). The time course of shoot net photosynthesis (A), stomatal conductance to water vapor (g_s), intercellular CO₂ concentration (C_i) and root respiration (R_s) were determined on a whole-plant basis. Root cooling caused a 25% reduction in A at high PPFD, which was preceded by more than 50% reduction of g_s and about 10% reduction in C_i. A versus C_i curves for single branches showed no difference between cold and warm soil temperatures, although stomatal conductance was lower for the lower soil temperature. This suggests that a stomatal limitation may have been involved in the inhibition of A. Furthermore, a concomitant decrease of as much as 23% in leaf relative water content (RWC) indicated that root cooling affected stomatal closure due to decreased water supply to the foliage. At lower PPFD, root cooling did not cause a decrease in A of the whole plant despite a moderate drop in g_s, C_i and RWC. Cold soil also led to a substantial and rapid reduction in root respiration rate (R_s) regardless of the light level.     

Shading reduces exploitation of soil nitrate and phosphate by Agropyron desertorum and Artemisia tridentata from soils with patchy and uniform nutrient distributions

 Shading may both lessen the demand for soil nutrients and also the energy supply for nutrient acquisition. Since root foraging for nutrients in patchy environments can be energy-costly, especially for an immobile nutrient such as phosphate (P), the effects of shading may be most expected in heterogeneous soils. Plant acquisition of nitrate (N) and phosphate from soils with patchy and uniform nutrient distributions was determined in a field study under open sunlight and with shading for two common perennial Great Basin shrub steppe species, Agropyron desertorum and Artemisia tridentata. Partial shading in a pattern which can occur in shrub steppe vegetation significantly decreased plant N and P acquisition from soils both in the patchy and the uniform nutrient treatments. Artemisia was more affected by the shading than was Agropyron. Exploitation of the rather immobile P ion by both species was reduced to a much greater degree by the shading in the patchy distribution treatment than in the uniform nutrient treatment. As expected, plant acquisition of the more mobile N varied little with nutrient distribution treatment for both species and the depression of N acquisition by shading was the same in both nutrient distributions. The effects of shading appeared to have had its primary influence on different components of root foraging in the two species, especially in the nutrient-rich patches. For Agropyron shading primarily affected root proliferation, as indicated by reduced root density in patches. For Artemisia, shading most influenced root physiological uptake capacity and this was most pronounced in the nutrient-rich patches. While aboveground competition for light may generally reduce nutrient acquisition, the effects appear to be most pronounced if root systems of these steppe species are foraging for nutrients such as P in spatially heterogeneous soils. Received: 29 February 1996 / Accepted: 16 July 1996     

Water supply and not nitrate concentration determines primary root growth in Arabidopsis

Understanding how root system architecture (RSA) adapts to changing nitrogen and water availability is important for improving acquisition. A sand rhizotron system was developed to study RSA in a porous substrate under tightly regulated nutrient supply. The RSA of Arabidopsis seedlings under differing nitrate (NO₃^‐) and water supplies in agar and sand was described. The hydraulic conductivity of the root environment was manipulated by using altered sand particle size and matric potentials. Ion‐selective microelectrodes were used to quantify NO₃^‐ at the surface of growing primary roots in sands of different particle sizes. Differences in RSA were observed between seedlings grown on agar and sand, and the influence of NO₃^‐ (0.1–10.0 mm ) and water on RSA was determined. Primary root length (PRL) was a function of water flux and independent of NO₃^‐. The percentage of roots with laterals correlated with water flux, whereas NO₃^‐ supply was important for basal root (BR) growth. In agar and sand, the NO₃^‐ activities at the root surface were higher than those supplied in the nutrient solution. The sand rhizotron system is a useful tool for the study of RSA, providing a porous growth environment that can be used to simulate the effects of hydraulic conductivity on growth.     

Response of Plant Height,Species Richness and Aboveground Biomass to Flooding Gradient along Vegetation Zones in Floodplain Wetlands,Northeast China

Flooding regime changes resulting from natural and human activity have been projected to affect wetland plant community structures and functions. It is therefore important to conduct investigations across a range of flooding gradients to assess the impact of flooding depth on wetland vegetation. We conducted this study to identify the pattern of plant height, species richness and aboveground biomass variation along the flooding gradient in floodplain wetlands located in Northeast China. We found that the response of dominant species height to the flooding gradient depends on specific species, i.e., a quadratic response for Carex lasiocarpa, a negative correlation for Calamagrostis angustifolia, and no response for Carex appendiculata. Species richness showed an intermediate effect along the vegetation zone from marsh to wet meadow while aboveground biomass increased. When the communities were analysed separately, only the water table depth had significant impact on species richness for two Carex communities and no variable for C. angustifolia community, while height of dominant species influenced aboveground biomass. When the three above-mentioned communities were grouped together, variations in species richness were mainly determined by community type, water table depth and community mean height, while variations in aboveground biomass were driven by community type and the height of dominant species. These findings indicate that if habitat drying of these herbaceous wetlands in this region continues, then two Carex marshes would be replaced gradually by C. angustifolia wet meadow in the near future. This will lead to a reduction in biodiversity and an increase in productivity and carbon budget. Meanwhile, functional traits must be considered, and should be a focus of attention in future studies on the species diversity and ecosystem function in this region.     

Topographic position and water chemistry of fens in a Dutch river plain

Abstract. On the Vecht river plain (western Netherlands), small fens, remnants of a large mesotrophic wetland bordering a moraine, of 1 to 5 ha are found in a man-made matrix of lakes and pastures. The regional position of the fens, local position of sampling sites, composition of the vegetation and local hydrological variables were measured. Polders in the river plain produce a complex hydrology obscuring the regional zonation between moraine and river. Water supply and species composition are determined more by a site's regional than local position. High-productivity reedlands are abundant close to the river. Carex paniculata reedlands receive large amounts of river water, which gives their fen water a high K⁺ concentration. Low-productivity C. diandra fens and litter fens have their optimum closer to the moraine. C. diandra fens are fed mainly by inflowing nutrient-poor ground- or surface water; litter fens receive primarily rainwater. Nutrients in fen water and in peat are lowest in C. diandra and C. lasiocarpa fens, but do not differ significantly between the communities. In both, iron seems to be more important than calcium in reducing phosphate solubility. Iron richness in the C. diandra fens is caused by present inflows of ground- or surface water, while in C. lasiocarpa fens, which succeed the former, iron richness is the result of historical inflows.     

A chromosome-scale Gastrodia elata genome and large-scale comparative genomic analysis indicate convergent evolution by gene loss in mycoheterotrophic and parasitic plants

Mycoheterotrophic and parasitic plants are heterotrophic and parasitize on fungi and plants, respectively, to obtain nutrients. Large-scale comparative genomics analysis has not been conducted in mycoheterotrophic or parasitic plants or between these two groups of parasites. We assembled a chromosome-level genome of the fully mycoheterotrophic plant Gastrodia elata (Orchidaceae) and performed comparative genomic analyses on the genomes of G. elata and four orchids (initial mycoheterotrophs), three parasitic plants (Cuscuta australis, Striga asiatica, and Sapria himalayana), and 36 autotrophs from various angiosperm lineages. It was found that while in the hemiparasite S. asiatica and initial mycoheterotrophic orchids, approximately 4–5% of the conserved orthogroups were lost, the fully heterotrophic G. elata and C. australis both lost approximately 10% of the conserved orthogroups, indicating that increased heterotrophy is positively associated with gene loss. Importantly, many genes that are essential for autotrophs, including those involved in photosynthesis, the circadian clock, flowering time regulation, immunity, nutrient uptake, and root and leaf development, were convergently lost in both G. elata and C. australis. The high-quality genome of G. elata will facilitate future studies on the physiology, ecology, and evolution of mycoheterotrophic plants, and our findings highlight the critical role of gene loss in the evolution of plants with heterotrophic lifestyles.